Remove data_frozen node role (tier) and frozen ILM phase (elastic#62403)

With the differentiation between searchable snapshots on the cold phase and searchable snapshots on
the frozen phase not implemented, there is no need to have a separate phase/tier for now. This
commit removes the frozen phase and tier, which can be added back at a later time.

(this tier was never in a released version, so this is not a breaking change)

Relates to elastic#60983
Relates to elastic#60994
Relates to elastic#60848

docs/reference/ilm/actions/ilm-allocate.asciidoc

@@ -2,7 +2,7 @@
 [[ilm-allocate]]
 === Allocate
 
-Phases allowed: warm, cold, frozen.
+Phases allowed: warm, cold.
 
 Updates the index settings to change which nodes are allowed to host the index shards
 and change the number of replicas.

docs/reference/ilm/actions/ilm-freeze.asciidoc

@@ -2,7 +2,7 @@
 [[ilm-freeze]]
 === Freeze
 
-Phases allowed: cold, frozen.
+Phases allowed: cold.
 
 <<frozen-indices, Freezes>> an index to minimize its memory footprint.
 

docs/reference/ilm/actions/ilm-searchable-snapshot.asciidoc

@@ -2,7 +2,7 @@
 [[ilm-searchable-snapshot]]
 === Searchable snapshot
 
-Phases allowed: cold, frozen.
+Phases allowed: cold.
 
 Takes a snapshot of the managed index in the configured repository
 and mounts it as a searchable snapshot.

docs/reference/ilm/actions/ilm-set-priority.asciidoc

@@ -2,7 +2,7 @@
 [[ilm-set-priority]]
 === Set priority
 
-Phases allowed: hot, warm, cold, frozen.
+Phases allowed: hot, warm, cold.
 
 Sets the <<recovery-prioritization, priority>> of the index as
 soon as the policy enters the hot, warm, or cold phase. 

docs/reference/ilm/actions/ilm-unfollow.asciidoc

@@ -2,7 +2,7 @@
 [[ilm-unfollow]]
 === Unfollow
 
-Phases allowed: hot, warm, cold, frozen.
+Phases allowed: hot, warm, cold.
 
 Converts a {ref}/ccr-apis.html[{ccr-init}] follower index into a regular index. 
 This enables the shrink, rollover, and searchable snapshot actions

docs/reference/ilm/ilm-index-lifecycle.asciidoc

@@ -6,16 +6,13 @@
 <titleabbrev>Index lifecycle</titleabbrev>
 ++++
 
-{ilm-init} defines five index lifecycle _phases_:
+{ilm-init} defines four index lifecycle _phases_:
 
 * **Hot**: The index is actively being updated and queried.
 * **Warm**: The index is no longer being updated but is still being queried.
 * **Cold**: The index is no longer being updated and is seldom queried. The
 information still needs to be searchable, but it's okay if those queries are
 slower.
-* **Frozen**: The index is no longer being updated and is seldom queried. The
-queries are performing longer-term analyses for which a slower response is
-acceptable.
 * **Delete**: The index is no longer needed and can safely be removed.
 
 An index's _lifecycle policy_ specifies which phases 
@@ -97,14 +94,6 @@ the rollover criteria, it could be 20 minutes before the rollover is complete.
 ifdef::permanently-unreleased-branch[]
   - <<ilm-searchable-snapshot, Searchable Snapshot>>
 endif::[]
-* Frozen
-  - <<ilm-set-priority-action,Set Priority>>
-  - <<ilm-unfollow-action,Unfollow>>
-  - <<ilm-allocate,Allocate>>
-  - <<ilm-freeze,Freeze>>
-ifdef::permanently-unreleased-branch[]
-  - <<ilm-searchable-snapshot, Searchable Snapshot>>
-endif::[]
 * Delete
   - <<ilm-wait-for-snapshot-action,Wait For Snapshot>>
   - <<ilm-delete,Delete>>

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/DataTier.java

@@ -20,7 +20,7 @@
 
 /**
  * The {@code DataTier} class encapsulates the formalization of the "content",
- * "hot", "warm", "cold", and "frozen" tiers as node roles. In contains the
+ * "hot", "warm", and "cold" tiers as node roles. In contains the
  * roles themselves as well as helpers for validation and determining if a node
  * has a tier configured.
  *
@@ -33,7 +33,6 @@ public class DataTier {
     public static final String DATA_HOT = "data_hot";
     public static final String DATA_WARM = "data_warm";
     public static final String DATA_COLD = "data_cold";
-    public static final String DATA_FROZEN = "data_frozen";
 
     /**
      * Returns true if the given tier name is a valid tier
@@ -42,8 +41,7 @@ public static boolean validTierName(String tierName) {
         return DATA_CONTENT.equals(tierName) ||
             DATA_HOT.equals(tierName) ||
             DATA_WARM.equals(tierName) ||
-            DATA_COLD.equals(tierName) ||
-            DATA_FROZEN.equals(tierName);
+            DATA_COLD.equals(tierName);
     }
 
     /**
@@ -131,23 +129,6 @@ public boolean canContainData() {
         }
     };
 
-    public static DiscoveryNodeRole DATA_FROZEN_NODE_ROLE = new DiscoveryNodeRole("data_frozen", "f") {
-        @Override
-        public boolean isEnabledByDefault(final Settings settings) {
-            return false;
-        }
-
-        @Override
-        public Setting<Boolean> legacySetting() {
-            return null;
-        }
-
-        @Override
-        public boolean canContainData() {
-            return true;
-        }
-    };
-
     public static boolean isContentNode(DiscoveryNode discoveryNode) {
         return discoveryNode.getRoles().contains(DATA_CONTENT_NODE_ROLE) || discoveryNode.getRoles().contains(DiscoveryNodeRole.DATA_ROLE);
     }
@@ -164,10 +145,6 @@ public static boolean isColdNode(DiscoveryNode discoveryNode) {
         return discoveryNode.getRoles().contains(DATA_COLD_NODE_ROLE) || discoveryNode.getRoles().contains(DiscoveryNodeRole.DATA_ROLE);
     }
 
-    public static boolean isFrozenNode(DiscoveryNode discoveryNode) {
-        return discoveryNode.getRoles().contains(DATA_FROZEN_NODE_ROLE) || discoveryNode.getRoles().contains(DiscoveryNodeRole.DATA_ROLE);
-    }
-
     /**
      * This setting provider injects the setting allocating all newly created indices with
      * {@code index.routing.allocation.include._tier: "data_hot"} unless the user overrides the

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/XPackPlugin.java

@@ -426,8 +426,7 @@ public Set<DiscoveryNodeRole> getRoles() {
             DataTier.DATA_CONTENT_NODE_ROLE,
             DataTier.DATA_HOT_NODE_ROLE,
             DataTier.DATA_WARM_NODE_ROLE,
-            DataTier.DATA_COLD_NODE_ROLE,
-            DataTier.DATA_FROZEN_NODE_ROLE));
+            DataTier.DATA_COLD_NODE_ROLE));
     }
 
     @Override

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/TimeseriesLifecycleType.java

@@ -34,30 +34,25 @@ public class TimeseriesLifecycleType implements LifecycleType {
     static final String HOT_PHASE = "hot";
     static final String WARM_PHASE = "warm";
     static final String COLD_PHASE = "cold";
-    static final String FROZEN_PHASE = "frozen";
     static final String DELETE_PHASE = "delete";
-    static final List<String> VALID_PHASES = Arrays.asList(HOT_PHASE, WARM_PHASE, COLD_PHASE, FROZEN_PHASE, DELETE_PHASE);
+    static final List<String> VALID_PHASES = Arrays.asList(HOT_PHASE, WARM_PHASE, COLD_PHASE, DELETE_PHASE);
     static final List<String> ORDERED_VALID_HOT_ACTIONS = Arrays.asList(SetPriorityAction.NAME, UnfollowAction.NAME, RolloverAction.NAME,
         ForceMergeAction.NAME);
     static final List<String> ORDERED_VALID_WARM_ACTIONS = Arrays.asList(SetPriorityAction.NAME, UnfollowAction.NAME, ReadOnlyAction.NAME,
         AllocateAction.NAME, ShrinkAction.NAME, ForceMergeAction.NAME);
     static final List<String> ORDERED_VALID_COLD_ACTIONS = Arrays.asList(SetPriorityAction.NAME, UnfollowAction.NAME, AllocateAction.NAME,
         FreezeAction.NAME, SearchableSnapshotAction.NAME);
-    static final List<String> ORDERED_VALID_FROZEN_ACTIONS = Arrays.asList(SetPriorityAction.NAME, UnfollowAction.NAME, AllocateAction.NAME,
-        FreezeAction.NAME, SearchableSnapshotAction.NAME);
     static final List<String> ORDERED_VALID_DELETE_ACTIONS = Arrays.asList(WaitForSnapshotAction.NAME, DeleteAction.NAME);
     static final Set<String> VALID_HOT_ACTIONS = Sets.newHashSet(ORDERED_VALID_HOT_ACTIONS);
     static final Set<String> VALID_WARM_ACTIONS = Sets.newHashSet(ORDERED_VALID_WARM_ACTIONS);
     static final Set<String> VALID_COLD_ACTIONS = Sets.newHashSet(ORDERED_VALID_COLD_ACTIONS);
-    static final Set<String> VALID_FROZEN_ACTIONS = Sets.newHashSet(ORDERED_VALID_FROZEN_ACTIONS);
     static final Set<String> VALID_DELETE_ACTIONS = Sets.newHashSet(ORDERED_VALID_DELETE_ACTIONS);
     private static Map<String, Set<String>> ALLOWED_ACTIONS = new HashMap<>();
 
     static {
         ALLOWED_ACTIONS.put(HOT_PHASE, VALID_HOT_ACTIONS);
         ALLOWED_ACTIONS.put(WARM_PHASE, VALID_WARM_ACTIONS);
         ALLOWED_ACTIONS.put(COLD_PHASE, VALID_COLD_ACTIONS);
-        ALLOWED_ACTIONS.put(FROZEN_PHASE, VALID_FROZEN_ACTIONS);
         ALLOWED_ACTIONS.put(DELETE_PHASE, VALID_DELETE_ACTIONS);
     }
 
@@ -146,9 +141,6 @@ public List<LifecycleAction> getOrderedActions(Phase phase) {
             case COLD_PHASE:
                 return ORDERED_VALID_COLD_ACTIONS.stream().map(a -> actions.getOrDefault(a, null))
                     .filter(Objects::nonNull).collect(Collectors.toList());
-            case FROZEN_PHASE:
-                return ORDERED_VALID_FROZEN_ACTIONS.stream().map(a -> actions.getOrDefault(a, null))
-                    .filter(Objects::nonNull).collect(Collectors.toList());
             case DELETE_PHASE:
                 return ORDERED_VALID_DELETE_ACTIONS.stream().map(a -> actions.getOrDefault(a, null))
                     .filter(Objects::nonNull).collect(Collectors.toList());
@@ -170,9 +162,6 @@ public String getNextActionName(String currentActionName, Phase phase) {
         case COLD_PHASE:
             orderedActionNames = ORDERED_VALID_COLD_ACTIONS;
             break;
-        case FROZEN_PHASE:
-            orderedActionNames = ORDERED_VALID_FROZEN_ACTIONS;
-            break;
         case DELETE_PHASE:
             orderedActionNames = ORDERED_VALID_DELETE_ACTIONS;
             break;